1. Field of the Invention
The present invention relates to the field of video-on-demand servers and systems and content management for video-on-demand servers.
2. Description of the Related Art
Delivery of client selected video content directly to a subscriber at a time chosen by the subscriber via a cable TV or other distribution network is a fast growing segment of the entertainment industry known as Video-on-Demand or VOD. The industry is enabled by new technology but sales are driven by the availability of up-to-date content demanded by consumers.
Subscribers of VOD are quite demanding and expect excellent performance from VOD systems. This is especially true for advanced VOD systems such as Interactive Video on Demand (IVOD) in which a user can manipulate the video, such as stopping, rewinding, pausing or fast forwarding. With increasing demand for VOD services, system operators are faced with difficult challenges. VOD systems have a finite storage capacity, which is dependent upon the capacity of video servers distributed throughout the system. Further, within a VOD system there are multiple storage locations relative to the proximity of a subscriber where VOD content files may be stored; content may be stored at a VOD server very close to the subscriber (such as at the node), farther from the subscriber (such as at a headend), or still farther from the subscriber (such as at a region center or cable library).
The storage capacity varies by server, and the server storage capacity at a particular location will be based, at least in part, upon the number of subscribers, subscriber characteristics, demand/usage patterns, etc. Thus, portions of a VOD system will have smaller capacity servers and therefore cannot store as much content or provide the content as readily as portions which have larger capacity servers. Although storage capacity can be expanded, such expansion imposes additional costs to the system operator which, in most cases, cannot be readily passed on to the customer. Thus, the system operator is faced with the challenge of managing and storing content files in the VOD system in a way that provides adequate performance at a reasonable cost.
The least expensive way to store content is to keep as much content as possible at the library server because this server can distribute the content to the largest number of subscribers. This reduces the cost of storage as the System operator does not need to purchase as much storage capacity for the other downstream servers. In so doing, a System operator takes advantage of his “economy of scale” in that the greatest number of subscribers has access to the content. However, location of content may impact performance. Content stored far away from subscribers on library servers may result in decreased performance for the subscriber as the content may be unavailable immediately upon request and/or there may be noticeable latencies (delay times) in delivering the content from the distant storage, or there may be unacceptable system demands in moving massive amounts of content to the subscribers at high-load time periods. It is difficult for a system operator to manage this tradeoff between cost and performance in storing content files especially when the demand for different content varies rapidly over time.
Thus there is a need for a system that efficiently manages the storage of video content files within various storage segments of a VOD system so as to provide acceptable performance to the subscribers at a reasonable cost to the system operator.